Optimization Suppression Method for FMCW Radar Transmitter-Receiver Leakage and Stationary Clutter

Abstract

A method for optimizing the suppression of FMCW radar transceiver leakage and stationary clutter is provided, wherein the analog anti-interference signal generated after analog memory calibration and the real-time intermediate frequency signal are subjected to difference and amplification processing in the analog domain as analog memory compensation; the digital anti-interference signal generated after digital memory calibration and the real-time digital intermediate frequency signal after analog memory compensation are subjected to difference processing in the digital domain as digital memory compensation, thereby finally achieving deep compensation for transceiver leakage and stationary clutter. The present invention utilizes the characteristics that the transceiver leakage and environmental clutter of the FMCW radar are superimposed on the intermediate frequency signal, and realizes comprehensive and deep suppression of transceiver leakage and environmental clutter at the same time by performing analog memory feedback compensation and digital memory feedback compensation on the intermediate frequency signal.

Description

Technical Field

[0001] The present invention relates to a technology in the field of frequency modulated continuous wave radar (FMCW) detection, specifically to an optimization suppression method based on digital-analog hybrid memory compensation for transceiver leakage and stationary clutter faced by FMCW radar during short-range detection. Background Art

[0002] There are two existing methods for the transceiver leakage problem of FMCW radar: RF cancellation and intermediate frequency compensation. However, RF cancellation can usually only suppress leakage of 1 to 2 frequency points and cannot achieve broadband, while intermediate frequency compensation only compensates for the leakage of the modulated signal and cannot compensate for other components such as antenna coupling leakage and mixer leakage. Traditionally, the problem of ambient clutter is generally removed through digital filtering, but in short-range detection, the target and environmental clutter are usually very close in the spectrum, or even overlap, making it difficult to filter out. In general, the above traditional technologies can only partially suppress transceiver leakage, or partially suppress environmental clutter, and cannot fully suppress transceiver leakage and clutter. Summary of the invention

[0003] Aiming at the deficiency that the prior art can only partially suppress the transceiver leakage and partially suppress the environmental clutter, the present invention proposes an optimized suppression method for the transceiver leakage and stationary clutter of FMCW radar, and utilizes the characteristic that the transceiver leakage and environmental clutter of FMCW radar are superimposed on the intermediate frequency signal, and realizes comprehensive and deep suppression of the transceiver leakage and environmental clutter by performing analog memory feedback compensation and digital memory feedback compensation on the intermediate frequency signal.

[0004] The present invention is achieved through the following technical methods:

[0005] The invention relates to an optimization suppression method for FMCW radar transceiver leakage and stationary clutter. The method comprises the following steps: subtracting an analog anti-interference signal generated after analog memory calibration from a real-time intermediate frequency signal in an analog domain and amplifying the signal as analog memory compensation; and then subtracting a digital anti-interference signal generated after digital memory calibration from a real-time analog memory compensated digital intermediate frequency signal in a digital domain as digital memory compensation, thereby finally realizing deep compensation for transceiver leakage and stationary clutter.

[0006] The analog memory calibration means that when there is no detection target in front of the radar, the intermediate frequency signal is collected and stored as an interference signal, and then the stored interference signal is synchronized with the intermediate frequency signal collected in real time in the digital domain, and output through digital-to-analog conversion as an analog anti-interference signal.

[0007] The digital memory calibration means that when there is no detection target in front of the radar, the intermediate frequency signal after analog memory compensation collected and stored is used as the residual interference signal, and is synchronized with the digital intermediate frequency signal after analog memory compensation collected in real time as the digital anti-interference signal.

[0008] The synchronization includes synchronization based on spectrum or synchronization based on modulation signal.

[0009] The spectrum-based synchronization includes:

[0010] ①Mark the stored interference signal or the remaining interference signal as s br (n), mark the real-time input signal as s bx (n); let i = 1, CR = t 0 f s , t 0 is the pulse repetition period of the radar front end, f s is the sampling rate;

[0011] ②Mark bx The first to CR points of (n) are s bx1 (p), label s br (n) The i-th to (CR+i-1)th point is s bri (p), subtract the two to get: s bti (p) = s bx1 (p)-s bri (p);

[0012] ③To s bti (p) Perform fast Fourier transform to obtain S bti (f), take Frequency range S bti (f) Maximum value, i.e. S max (i);

[0013] ④Let i=i+1, and repeat steps ②③ until i=CR, and get array S max ;

[0014] ⑤ Take S max The horizontal coordinate p of the minimum value t , then we get the same signal as the real-time input signal s bx (n) The synchronized anti-interference signal is s br (n+p t -1).

[0015] The synchronization based on the modulation signal includes:

[0016] i. Mark the stored interference signal or the remaining interference signal as s br (n), and its corresponding modulation signal is s z(n). The real-time collected signal is marked as s bx (n), and its corresponding real-time modulation signal is s zx (n);

[0017] ii. For s z (n) Take the difference and get: s zd (n) = s z (n)-s z (n-1), find s zd (n) Mean Where N is s z (n) length. Take s zd (n)>3s d The minimum horizontal coordinate of a point p z .

[0018] iii. For s zx (n) Take the difference and get: s zdx (n) = s zx (n)-s zx (n-1), take s zdx (n)>3s d The minimum horizontal coordinate of a point p zx .

[0019] iv. With real-time input signals bx (n) The synchronized anti-interference signal is s br (n+p z -p zx ).

[0020] Technical Effects

[0021] The present invention adds analog memory compensation on the basis of digital compensation, and the two complement each other to achieve deep compensation for interference and improve the signal-to-noise ratio.

[0022] Compared with the prior art, the present invention achieves comprehensive and deep compensation for interference through two-step compensation in the analog and digital domains. At the same time, analog memory compensation reduces the influence of quantization noise in the sampling process, thereby improving the signal-to-noise ratio of the digital signal. In general, the present invention effectively improves the detection capability and detection effect of the FMCW radar system at close range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the digital-analog hybrid compensation method;

[0024] Figure 2 Calibration process diagram for the mixed analog-digital method

[0025] Figure 3 It is a schematic diagram of a synchronization method based on a modulation signal;

[0026] Figure 4 Figure 1. Setup diagram for interference suppression experiment.

[0027] Figure 5 This is the distance result diagram of the interference suppression experiment;

[0028] Figure 6 Figure 1. Setup diagram for the gesture detection experiment.

[0029] Figure 7 This is the distance result diagram of the gesture detection experiment;

[0030] Figure 8 This is the distance-Doppler result diagram of the gesture detection experiment; DETAILED DESCRIPTION

[0031] like Figure 1 As shown, it is an implementation scenario of this embodiment, including: an FMCW radar composed of a transmitting antenna, a receiving antenna, and a radar front end, and an optimized suppression system for FMCW radar transceiver leakage and stationary clutter involved in this embodiment, including: an analog subtractor, an analog amplifier, a digital-to-analog converter (ADC), an analog-to-digital converter (DAC) and a microcontroller unit (MCU), wherein: the analog subtractor and the analog amplifier receive a receiving signal from the FMCW radar, and output an analog memory compensation signal to the ADC after analog memory compensation calibration, the MCU outputs a digital anti-interference signal to the DAC after digital memory compensation calibration, and the DAC outputs the analog anti-interference signal to the analog subtractor to achieve optimized suppression.

[0032] The analog memory compensation calibration process includes:

[0033] ① Figure 1 The virtual single-shot three-throw switch in the radar is set to S1, the detection target is moved out of the radar detection range, the DAC output is set to 0V, and the amplifier gain is set to 1. At this time, the signal sampled by the ADC is the interference signal s b0 (t);

[0034] ② Sample and store a section of interference signal s b0 (n) (e.g. 10 pulse repetition cycles), then disconnect S1;

[0035] ③Through Figure 3 The spectrum-based synchronization method shown or Figure 4 The modulation signal based synchronization method shown in the figure converts the stored interference signal s b0 (n) and the real-time received raw intermediate frequency signal s b (n) synchronization, and then set the DAC output to the cycle of the interference signal after synchronization, and the output signal is the analog anti-interference signal

[0036] ④Through analog subtractor From the real-time raw IF signal s b (t)(=s b0 (t)) is subtracted. Due to the limited accuracy of the analog-to-digital converter ADC and the digital-to-analog converter DAC, and b0 (t) will not be exactly the same, there will be residual interference signal after the subtractor The residual interference signal is amplified by the analog amplifier A times and becomes the analog residual interference signal

[0037] The digital memory compensation calibration process includes:

[0038] ① Figure 1 The virtual single-shot three-throw switch jumps to S2, keeping the radar without detecting targets in front of it, sampling and recording the remaining interference signals of several pulse repetition cycles. As disconnect S2;

[0039] ② The recorded residual interference signal is synchronized with the real-time sampled signal as a digital anti-interference signal, which is subtracted from the real-time sampled signal to achieve depth compensation.

[0040] The normal working process includes: Figure 1 The virtual single-shot three-throw switch in the radar jumps to S3, keeping the analog memory and digital memory unchanged, and moving the detection target into the radar detection range to detect it. The signal flow for normal operation is Figure 1 The original intermediate frequency signal is s b (t) = s bM (t)+s b0 (t), where: s bM (t) is the detection target signal, s b0 (t) is the interference signal. The original intermediate frequency signal s b (t) and analog anti-interference signal Subtract and amplify to complete analog memory compensation and obtain the preliminary compensation signal The preliminary compensation signal is converted into a digital signal by ADC And with digital anti-interference signal Subtracting, completing the digital memory compensation, and obtaining the depth compensated signal As bM (n). It is particularly important to note that for synchronous sampling radar systems (the radar front end and ADC have the same clock source), the analog memory and digital memory only need to be calibrated once. For asynchronous sampling radar systems (the radar front end and ADC have different clock sources), the analog memory and digital memory need to be calibrated again after working for a period of time, depending on the radar situation, usually at an interval of 5 minutes.

[0041] The synchronization is achieved by Figure 3 The spectrum-based synchronization method shown or Figure 4 The synchronization method based on the modulation signal is shown.

[0042] like Figure 3 As shown, the spectrum-based synchronization method includes: ① marking the stored interference signal or the remaining interference signal as s br (n), mark the real-time input signal as s bx (n). Let i = 1, CR = t 0 f s , t 0 is the pulse repetition period of the radar front end, f s is the sampling rate. ② Mark s bx The first to CR points of (n) are s bx1 (p), label s br (n) The i-th to (CR+i-1)th point is s bri (p), subtract the two to get: s bti (p) = s bx1 (p)-s bri (p). ③ For s bti (p) Perform fast Fourier transform to obtain S bti (f) Frequency range S bti (f) Maximum value, i.e. S max (i). ④ Let i = i + 1, and repeat steps ② and ③ until i = CR, and get the array S max ⑤ Take S max The horizontal coordinate p of the minimum value t , then we get the real-time input signal s bx (n) The synchronized anti-interference signal is s br (n+p t -1).

[0043] like Figure 4 As shown, the synchronization method based on modulation signal is different from the synchronization method based on spectrum in that: an additional modulation signal needs to be collected. Based on the principle of synchronization between the modulation signal and its corresponding intermediate frequency signal, the anti-interference signal can be synchronized with the real-time intermediate frequency signal by aligning the jump point of the reference modulation signal with the real-time modulation signal, which specifically includes:

[0044] i. Mark the stored interference signal or the remaining interference signal as s br (n), and its corresponding modulation signal is s z (n). The real-time collected signal is marked as s bx (n), and its corresponding real-time modulation signal is s zx (n);

[0045] ii. For s z 9n) Take the difference and get: s zd (n) = s z (n)-s z (n-1), find s zd (n) Mean Where N is s z (n) length. Take s zd (b)>3s d The minimum horizontal coordinate of a point p z .

[0046] iii. For s zx (n) Take the difference and get: s zdx (n0=s zx (n)-s zx (n-1), take s zdx (n)>3s d The minimum horizontal coordinate of a point p zx .

[0047] iv. With real-time input signals bx (n) The synchronized anti-interference signal is s br (n+p z -p zx ).

[0048] After specific actual experiments, this embodiment tests the interference suppression ability of this method by detecting the position of the target. The parameters of the radar front end are set as follows: sawtooth wave modulation, center frequency f c =79GHz, modulation bandwidth B = 4GHz, and pulse repetition period t 0 =6ms. Figure 5 As shown in (a), an iron cup is placed 15 cm away from the radar to generate environmental static clutter, and the detection target is a plastic bookend placed 28 cm away from the radar. Figure 6 As shown in the figure, the interference suppression effect of the digital-analog hybrid compensation method is shown. It can be seen that after analog memory compensation, the transceiver leakage is suppressed by 24.7dB, and the static clutter is suppressed by 17.2dB. After digital memory compensation, the transceiver leakage is further suppressed by 13.8dB, reaching 38.5dB, and the static clutter is further suppressed by 8.2dB, reaching 25.4dB. At the same time, it can be observed that the noise is reduced by 10dB. This is because after analog memory compensation, the signal is further amplified, making full use of the dynamic range of the ADC and reducing the quantization noise.

[0049] like Figure 5As shown in (b), an iron cup is placed 15 cm away from the radar to generate environmental static clutter. The detection target is a palm with the palm facing the radar, about 28 cm away from the radar, making small movements back and forth. Figure 7 As shown in the figure, the interference suppression effect of the digital-analog hybrid compensation method is that after analog memory compensation, the transceiver leakage is suppressed by 21.9dB, and the static clutter is suppressed by 16.8dB. After digital memory compensation, the transceiver leakage is further suppressed by 14.6dB, reaching 35.5dB suppression, and the static clutter is further suppressed by 7.2dB, reaching 24dB suppression. At the same time, it can be observed that the noise has dropped by 5dB. This is because after analog memory compensation, the signal is further amplified, making full use of the dynamic range of the ADC and reducing the quantization noise. Figure 8 As shown, it is the distance-Doppler diagram of the intermediate frequency signal before and after the digital-analog hybrid memory compensation. It can be seen that after compensation, the "ghost" caused by the interference is removed, and the palm signal becomes more obvious, which is expected to increase the accuracy of applications such as gesture recognition.

[0050] Compared with the prior art, this method achieves comprehensive and deep compensation for interference through two-step compensation in the analog and digital domains. At the same time, analog memory compensation reduces the influence of quantization noise in the sampling process, thereby improving the signal-to-noise ratio of the digital signal. In general, the present invention effectively improves the detection capability and detection effect of the FMCW radar system at close range.

[0051] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. An optimized suppression method for FMCW radar transceiver leakage and stationary clutter, It is characterized in that The analog anti-interference signal generated after analog memory calibration is subtracted from the real-time intermediate frequency signal in the analog domain and amplified as analog memory compensation; the digital anti-interference signal generated after digital memory calibration is subtracted from the real-time digital intermediate frequency signal after analog memory compensation in the digital domain as digital memory compensation, and finally the deep compensation of the receiving and transmitting leakage and stationary clutter is realized; The analog memory calibration means: when there is no detection target in front of the radar, the intermediate frequency signal is collected and stored as an interference signal, and then the stored interference signal is synchronized with the intermediate frequency signal collected in real time in the digital domain, and outputted through digital-to-analog conversion as an analog anti-interference signal; The digital memory calibration means that when there is no detection target in front of the radar, the intermediate frequency signal after analog memory compensation collected and stored is used as the residual interference signal, and is synchronized with the digital intermediate frequency signal after analog memory compensation collected in real time as the digital anti-interference signal; The synchronization includes synchronization based on spectrum or synchronization based on modulation signal; The spectrum-based synchronization includes: ①Mark the stored interference signal or the remaining interference signal as s br (n), mark the real-time input signal as s bx (n); let i = 1, CR = t 0 f s , t 0 is the pulse repetition period of the radar front end, f s is the sampling rate; ②Mark bx The first to CR points of (n) are s bx1 (p), label s br (n) The i-th to (CR+i-1)th point is s bri (p), subtract the two to get: s bti (p) = s bx1 (p)-s bri (p); ③To s bti (p) Perform fast Fourier transform to obtain S bti (f) Frequency range S bti (f) Maximum value, i.e. S max (i); ④Let i=i+1, and repeat steps ②③ until i=CR, and get array S max ; ⑤ Take S max The horizontal coordinate p of the minimum value t , then we get the same signal as the real-time input signal s bx (n) The synchronized anti-interference signal is s br (n+p t -1); The synchronization based on the modulation signal includes: i. Mark the stored interference signal or the remaining interference signal as s br (n), and its corresponding modulation signal is s z (n); mark the real-time collected signal as s bx (n), and its corresponding real-time modulation signal is s zx (n); ii. For s z (n) Take the difference and get: s zd (n) = s z (n)-s z (n-1), find s zd (n) Mean Where N is s z (n) length; take s zd (n)>3s d The minimum horizontal coordinate of a point p z ; iii. For s zx (n) Take the difference and get: s zdx (n) = s zx (n)-s zx (n-1), take s zdx (n)>3s d The minimum horizontal coordinate of a point p zx ; iv. With real-time input signals bx (n) The synchronized anti-interference signal is s br (n+p z -p zx ).

2. An optimized suppression system for FMCW radar transceiver leakage and stationary clutter that implements the method of claim 1, include: An analog subtractor, an analog amplifier, a digital-to-analog converter, an analog-to-digital converter and a microcontroller unit, wherein: the analog subtractor and the analog amplifier receive a receiving signal from an FMCW radar, output an analog memory compensation signal to the ADC after analog memory compensation calibration, the MCU outputs a digital anti-interference signal to the DAC after digital memory compensation calibration, and the DAC outputs the analog anti-interference signal to the analog subtractor to achieve optimized suppression.

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